The size of components in classical computers is shrinking
exponentially, if trends continue soon the behavior of the components
will be dominated more by quantum physics than classical physics.
Researchers have begun investigating the implications of these quantum
behaviors on computation. Surprisingly it seems that a computer whose
components are able to function in a quantum manner are more powerful
than any classical computer can be.

The study of quantum physics has shown that the behaviors of physical
systems that understood from classical physics break down in systems
of sufficiently small scale. The scale which these classical
assumptions break down is the scale we are rapidly approaching with
components in modern computers. At the current rate of
miniaturization memory components will reach the size of about one
atom per bit around the year 2020. At this size the storage for a bit
cannot be expected to behave in a classical manner, and the size of an
elementary particle is an absolute lower bound for the classical bit
size. This bound does not hail the eventual end to advances in
computing hardware. The same quantum effects which will prevent the
continual miniaturization of classical computers may allow the
development of a quantum computer, which relies upon these quantum
effects.

At the heart of quantum computing lies parallelism. This inherent
parallelism, combined with the exponential slowdown in any classical
simulation of a quantum system make simulation of a quantum system an
ideal candidate for speedup through parallelism.